1. Field of the Invention
The invention relates to a magnetic transducer and a thin film magnetic head using the same. More particularly, the invention relates to a magnetic transducer and a thin film magnetic head using the same, which can be manufactured by a simple manufacturing process and can obtain good output.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive element (hereinafter referred to as an MR element) that is a type of magnetic transducer and a recording head having an inductive magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), and an element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect). The GMR film is mainly used in the MR element for the reproducing head whose surface recording density exceeds 3 Gbit/inch2. As the GMR film, a xe2x80x9cmultilayered type (antiferromagnetic type)xe2x80x9d film, an xe2x80x9cinductive ferromagnetic typexe2x80x9d film, a xe2x80x9cgranular typexe2x80x9d film, a xe2x80x9cspin valve typexe2x80x9d film and the like are proposed. Of these types of films, the spin valve type GMR film is used for the industrialization of a magnetic head.
The spin valve type GMR film has a stacked structure comprising a nonmagnetic layer; a magnetic layer having the fixed orientation of magnetization; and a magnetic layer having the orientation of magnetization changing in accordance with a signal magnetic field, in which the magnetic layers are stacked with the nonmagnetic layer in between. Electrical resistance changes in accordance with a relative angle between the orientations of magnetizations of the two magnetic layers. The spin valve type GMR film obtains the rate of resistance change of 2% to 6% (U.S. Pat. No. 5,408,377).
Moreover, a xe2x80x9ctunnel junction typexe2x80x9d GMR film utilizing a tunnel current passing through a thin insulating layer has been recently developed (U.S. Pat. No. 5,901,018). The tunnel junction type GMR film has a structure in which an insulating layer is sandwiched between two magnetic layers. During the passage of the tunnel current through the insulating layer, electrical resistance changes in accordance with the signal magnetic field. The tunnel junction type GMR film obtains higher electrical resistance as a junction area becomes smaller. However, shot noise is caused and thus the S/N (signal to noise) ratio becomes low. Consequently, the tunnel junction type GMR film has the limitations of improvement in properties of the magnetic head.
Therefore, attention has been recently paid to an MR element having the so-called CPP (Current Perpendicular to the Plane) structure in which a current is passed through the multilayered type GMR film in the direction of stacking (Japanese Unexamined Patent Application Publication No. Hei 5-275769). The multilayered type GMR film has a stack comprising magnetic layers stacked alternately with nonmagnetic layers. The orientations of magnetizations of the magnetic layers change in accordance with the signal magnetic field, and thus electrical resistance changes. The above-mentioned multilayered type GMR film is disclosed in, for example, Japanese Unexamined Patent Application Publication No. Hei 4-360009, Japanese Patent No. 2610376, Japanese Unexamined Patent Application Publication No. Hei 5-90026, Japanese Unexamined Patent Application Publication No. Hei 7-78316 and Japanese Unexamined Patent Application Publication No. Hei 9-180135. According to the multilayered type GMR film, the rate of resistance change is about 1% to 10% when the current is passed perpendicularly to the direction of stacking (Japanese Unexamined Patent Application Publication No. Hei 5-90026). The rate of resistance change is about 10% to 15% when the current is passed in the direction of stacking.
The above-described MR element has magnetic domain control layers for controlling the orientations of magnetizations of the magnetic layers in order to prevent so-called Barkhausen noise. For example, the multilayered type GMR film has a pair of magnetic domain control layers on both sides in the direction perpendicular to the direction of stacking of the GMR film (Japanese Unexamined Patent Application Publication No. Hei 9-180135).
However, a problem exists. A manufacturing process is complicated when the magnetic domain control layers are formed so as to sandwich the stack therebetween in the direction perpendicular to the direction of stack as described above. Another problem exists. It is preferable that the magnetic domain control layers are separated from the stack, because the rate of resistance change decreases when the current passing through the stack is diverted into the magnetic domain control layers. However, a magnetic domain cannot be sufficiently controlled in the above-mentioned arrangement.
It is an object of the invention to provide a magnetic transducer and a thin film magnetic head, which can be manufactured by a simple manufacturing process and can obtain good output.
A magnetic transducer of the invention comprises a stack having a plurality of magnetic layers stacked alternately with a plurality of nonmagnetic layers; and a magnetic domain control layer formed on at least one side of the stack in the direction of stacking, for controlling the orientations of magnetizations of the magnetic layers.
In a magnetic transducer of the invention, the orientations of magnetizations of the magnetic layers of the stack are controlled by the magnetic domain control layer.
Another magnetic transducer of the invention comprises a stack having a plurality of magnetic layers stacked alternately with a plurality of nonmagnetic layers; and a magnetic field applying layer formed on at least one side of the stack in the direction of stacking, for applying a magnetic field in a fixed direction to at least a part of the stack.
In another magnetic transducer of the invention, the magnetic field is applied to at least a part of the stack by the magnetic field applying layer. The orientations of magnetizations of the magnetic layers of the stack are controlled by the applied magnetic field.
Still another magnetic transducer of the invention comprises a stack having a plurality of magnetic layers stacked alternately with a plurality of nonmagnetic layers; and a layer having the fixed orientation of magnetization formed on at least one side of the stack in the direction of stacking and having magnetization fixed in a fixed direction.
In still another magnetic transducer of the invention, the orientations of magnetizations of the magnetic layers of the stack are controlled by action of the magnetization of the layer fixed in a fixed direction.
Preferably, the layer has an antiferromagnetic layer and an exchange coupling layer exchange coupling with the antiferromagnetic layer. Preferably, the antiferromagnetic layer is made of a material containing at least one element in a group including Pt (platinum), Ru (ruthenium), Rh (rhodium), Pd (palladium), Ni (nickel), Au (gold), Ag (silver), Cu (copper), Ir (iridium), Cr (chromium) and Fe (iron), and Mn (manganese).
Preferably, the exchange coupling layer is made of a material containing at least one element in a group including Fe, Co (cobalt) and Ni. Preferably, an inserted layer made of a nonmagnetic material is provided between the layer and the stack. Preferably, the inserted layer is made of a material containing at least one element in a group including Au, Ag, Cu, Ru, Rh, Re (rhenium), platinum and tungsten (W). Preferably, a thickness of the inserted layer is from 1 nm to 10 nm inclusive.
Preferably, the stack has a projecting portion facing a signal magnetic field. Preferably, a length of the projecting portion along the projecting direction thereof is 0.1 xcexcm or less. Preferably, a magnetic field capture (or take in) limiting portion for partially limiting an effect of a signal magnetic field is provided in an area on a side of the stack facing a signal magnetic field. Preferably, a magnetic field capture limiting portion made of a magnetic material is provided at a position corresponding to a part of the stack on a side of the stack facing a signal magnetic field.
Preferably, at least one of the plurality of magnetic layers contains a material containing at least Co in a group including Co, Fe and Ni, or a material containing at least Ni in a group including Ni, Co, Fe, Cr, Ta (tantalum), Rh (rhodium), Mo (molybdenum), Zr (zirconium) and Nb (niobium). Preferably, at least one of the plurality of magnetic layers includes a nickel-containing layer made of a material containing at least Ni in a group including Ni, Co, Fe, Cr, Ta, Rh, Mo, Zr and Nb, and a cobalt-containing layer made of a material containing at least Co in a group including Co, Fe and Ni.
Preferably, a thickness of each of the magnetic layers is from 1 nm to 6 nm inclusive. Preferably, the number of the magnetic layers is from 2 to 20 inclusive. Preferably, at least one of the nonmagnetic layers is made of a material containing at least one element in a group including Au, Ag, Cu, Ru, Rh, Re, Pt and W. Preferably, at least one of the nonmagnetic layers is made of a material containing Ni and Cr. Preferably, one of the nonmagnetic layers, which is located on one outermost side in the direction of stacking, is made of a material containing Ni and Cr.
Preferably, a thickness of each of the nonmagnetic layers is set so as to locally maximize antiferromagnetic coupling energy induced between two magnetic layers adjacent to each other with each of the nonmagnetic layers in between. Preferably, the antiferromagnetic coupling energy induced between two magnetic layers adjacent to each other with each of the nonmagnetic layers in between is from 0.1xc3x9710xe2x88x924 J/m2 to 2.0xc3x9710xe2x88x924 J/m2 inclusive.
Preferably, the stack has a plurality of regions into which the stack is divided in the direction of stacking, and at least two regions of the plurality of regions differ from each other in a material or composition of the magnetic layers. Preferably, the stack has a first region including the magnetic layers made of a material containing at least Ni in a group including Ni, Co, Fe, Cr, Ta, Rh, Mo, Zr and Nb, and a second region including the magnetic layers made of a material containing at least Co in a group including Ni, Co and Fe.
A thin film magnetic head of the invention has a magnetic transducer described above.
Preferably, a thin film magnetic head of the invention further comprises a current path for passing a current through the stack in the direction of stacking. Preferably, a thin film magnetic head further comprises a pair of shield layers for sandwiching the stack therebetween with a pair of gap layers in between, wherein the shield layers and the gap layers function as the current path.
Other and further objects, features and advantages of the invention will appear more fully from the following description.